System management communication functions, for features such as Intel® Active Management Technology (Intel® AMT), require the ability to always access a system management processor or microcontroller in various system states, such as when the system is on or when the system is in a sleep mode. The communications related to accessing and communicating with the system may need to occur independently of the system processors and software. Such independent communications are commonly referred to as “out-of-band” communications. The term “sideband” is used in this context may refer to when “in-band” and “out-of-band” communications both occur over a common medium.
Existing network controllers used for system management communication functions may include sideband interfaces based on specific technologies. For example, a network controller may be based on a system management bus utilizing inter-integrated circuit technology (SMBus/I2C). Three other alternative technologies on which a network controller may be based include a technology referred to as fast management link (FML), a technology referred to as reduced media-independent interface (RMII), or another technology referred to as serial peripheral interface (SPI). Each of these technologies, when used to provide sideband communication capabilities, has certain drawbacks.
Of these interface technologies SMBus/I2C provides a low pin-count, such as two pins, and is widely available in third party management controllers. However, SMBus/I2C lacks sufficient speed for effective support of manageability functions such as media redirection and video redirection. FML is faster but still lacks sufficient speed for video redirection per its present definition and is proprietary in nature. Being proprietary means that it is generally not available in third party management controllers. RMII and RMII-based interfaces are available as a standard, have the bandwidth to support video and media redirection, and are available in some third party management controllers. Unfortunately, RMII and RMII-based interfaces require a relatively high pin-count, such as six or seven pins. Additionally, RMII-based interfaces generally cannot be routed more than eight to ten inches. Even further, existing network controllers using these technologies require that the management controllers remain powered while the system is in a low-power state even though the management controllers are inactive. This limitation causes problems meeting energy conservation standards and directives.